FREEPORT, Ill. – Asian copperleaf, an emerging weed of concern in the Midwest, has now been confirmed in a second Illinois county. Following its initial discovery in Stephenson County during harvest in 2025, a newly confirmed population in Carroll County suggests that this species may be more widespread than previously believed.
Asian copperleaf is non-native to the United States. First documented in New York in 1990, additional populations were not confirmed until it was positively identified in an Iowa seed corn field in 2016. Since then, it has been found in twelve counties across Iowa, two counties in northwest Illinois, and southern Minnesota.
Fall is the best time to identify Asian copperleaf because it is in its reproductive stage when it has its most distinguishable features. It is commonly first noticed after harvest when a green “carpet” of weeds is left behind after the crop comes off. Key identification traits include alternate, lanceolate to egg-shaped leaves with bluntly serrated margins and deep veins, and heart-shaped bracts with shallow, blunt teeth that surround the flowers and are located along the stems.
Identifying and reporting populations is imperative to stopping the spread of Asian copperleaf. With the implementation of proper management, the movement of seed to additional fields can be reduced. If you suspect you have found Asian copperleaf, please contact Kathryn Seebruck (seebruck@illinois.edu or 815-986-4357) for assistance with identification. You can also make reports anonymously at go.illinois.edu/ACreport.
Find more information on Asian copperleaf identification and management in this fact sheet developed by University of Illinois Extension and Iowa State University Extension and Outreach.
Learn what has been discovered about Asian copperleaf in Iowa over the last ten years in this Talking Crop podcast episode with Meaghan Anderson, Iowa State University Extension and Outreach field agronomist. The episode can also be found on Apple Podcasts and Spotify.
University of Illinois Extension develops educational programs, extends knowledge, and builds partnerships to support people, communities, and their environments as part of the state's land-grant institution. Extension serves as the leading public outreach effort for University of Illinois Urbana-Champaign and the College of Agricultural, Consumer and Environmental Sciences in all 102 Illinois counties through a network of 27 multi-county units and over 500 staff statewide. Extension’s mission is responsive to eight strategic priorities — community, economy, environment, food and agriculture, health, partnerships, technology and discovery, and workforce excellence — that are served through five program areas — 4-H youth development, agriculture and agribusiness, community and economic development, health and community wellness, and natural resources, environment, and energy.